Electron beam sterilizing devices are known, which emits electrons to a web of material, such as a packaging laminate, for sterilization purposes. The level of sterilization is determined by the irradiation dose delivered onto the wall. If the delivered dose is too small the sterilization will not be adequate, and if the dose is too high the packaging laminate may be affected negatively. The negative effects include that the taste of the final product in a packaging container formed from the packaging laminate might be affected (off-taste problem) and that the packaging laminate may be deformed and/or damaged. The off-taste problem is obviously a problem to consider if the packaging laminate is to be used as a container for foodstuff, such as beverage.
The irradiation dose will be affected by, among other things, the irradiation intensity and the irradiation time. It will also be affected by the distance between the electron beam sterilizing device exit and the surface to be irradiated.
In a situation where all parameters can be varied without constraint, the problem of sterilizing packaging laminate by means of an electron beam is not a difficult task. However, in a modern foodstuff processing plant, where thousands and thousands of packaging containers are to be manufactured, sterilized, filled, and sealed in a rapid pace, the conditions are quite different. For instance, the required pace is high, and the sterilising machine thus has to operate fast.
Packaging laminate is generally provided to a filling station in large rolls of material. The rolls are unwound and led as a web to the actual location where packaging containers are formed, filled and sealed. The web of packaging laminate may be sterilized by the above electron irradiation. One immediate issue in this process is the occurrence of standstills. If no actions are taken a standstill it will result in that the same area of the web being irradiated for an overly long period of time, inevitably resulting in destruction of the material, which may lead to material failure or off-taste problems.
The general idea, as well as specific embodiments of the above is described in WO04/110868 by the present applicant.
The present invention may also be utilized in an electron beam sterilizing device for sterilisation of individual packaging containers, having an additional benefit.